<h3>Categories</h3>
<ul id="categories">
    {% with active_categories as cats %}
        {% for c in cats %}
            <li>
            {% ifequal c.get_absolute_path request_path %}
                {{ c.name }}<br>
            {% else %}
                <a href="{{ c.get_absolute_url }}" class="category">{{ c.name }}</a><br>
            {% endifequal %}
            </li>
        {% endfor %}
    {% endwith %}
</ul>